Typically, a folding type of mobile terminal device has a first housing that is provided with operation keys and a second housing that is provided with a display device. The housings are joined such that they are able to be opened and closed via a hinge portion and comprise a type of mobile terminal device (i.e., a mobile instrument). In this mobile terminal device, a flexible printed wiring board is provided via a cavity located in the hinge portion in order to electrically connect together circuit substrates built into each housing.
As is disclosed, for example, in Japanese Patent No. 3093727, a portion of a conventional flexible printed wiring board that is wound in a spiral configuration is positioned inside a cavity of a hinge portion. In addition, as is disclosed, for example, in Japanese Patent Application Laid-Open (JP-A) No. 06-311216, wires such as antenna wiring are passed through the inner diameter resulting when the flexible printed wiring board is wound in a spiral configuration in order to electrically connect a transmitting/receiving unit located in one housing with an antenna located in another housing.
However, in order to wind a flexible printed wiring board in a spiral configuration so as to position it inside a hinge cavity during the assembly of a mobile telephone, each flexible printed wiring board has to be wound individually by hand. Accordingly, this is time consuming and gives rise to poor work efficiency. Moreover, because the wind radius of a spirally wound flexible printed wiring board varies due to the tensile force imparted thereto when the housings are opened and closed, it is necessary to ensure that excessive force does not act on localized areas of the flexible printed wiring board. Furthermore, if excessive force does not act on localized areas of the flexible printed wiring board due to some particular cause when the flexible printed wiring board is simply wound in a spiral configuration inside the cavity in a conventional manner, there is a possibility that the soundness of the flexible printed wiring board will be impaired, such as bends and the like occurring in the flexible printed wiring board.
The entire cavity of the hinge portion is formed as one cylinder by placing curved surface portions of circular arc shaped plates that are provided at end portions of both housings alternating in the transverse direction of the housings. Because adjacent curved surface portions are moved relative to each other by the opening or closing of the casings, a slight gap is provided between the adjacent curved surface portions. Therefore, moisture may penetrate inside the housings from this gap. If moisture penetrates into the hinge portion, there is a possibility that this moisture will travel over the flexible printed wiring board located inside the hinge portion and will reach a circuit substrate built into the housing.
In cases where moisture penetrates to the circuit substrate, the proper operation of circuits and electronic components on the substrate is compromised. In order to solve this problem, as is disclosed, for example, in JP-A No. 2002-124779, a structure is known in which this spirally wound flexible printed wiring board is sandwiched between nipping members provided in each of the two housings. The nipping members prevent moisture from traveling along the flexible printed wiring board from the gap in the hinge portion and penetrating the hinge portion, and prevent shorts and corrosion of electronic components on a substrate on the housing side. These nipping members are formed by members having elasticity such as urethane, rubber, or sponge bodies.
However, this structure is not sufficient to prevent moisture from penetrating into the interior of the housing because the structure still allows the actual penetration of moisture into the cavity.